Low back reflection echelle grating

Abstract

Embodiments of the present disclosure are directed toward an optical apparatus that includes a semiconductor layer to propagate light from at least one light source. The optical apparatus may further include a curved echelle grating with a plurality of grating teeth, the echelle grating at an outer side of the semiconductor layer. The curved echelle grating may include a plurality of grating teeth, and a grating tooth of the plurality of grating teeth may have a grating facet and a shadow facet. A shadow facet may have an angle of grating greater than 0 degrees with respect to a normal of a curve of the curved echelle grating. Other embodiments may be described and/or claimed.

What is claimed is: 
     
       1. An optical apparatus comprising:
 a semiconductor layer to propagate a light from a waveguide; and 
 a curved echelle grating at an outer side of the semiconductor layer; 
 wherein the curved echelle grating includes a plurality of grating teeth, a grating tooth of the plurality of grating teeth with a grating facet and a shadow facet, wherein the light from the waveguide strikes the shadow facet of the grating tooth, and then is reflected in a direction not directly towards the waveguide to reduce interference with the light from the waveguide, and respective shadow facets have an angle of grating greater than 0 degrees and less than approximately 60 degrees with respect to a normal of a curve of the curved echelle grating. 
 
     
     
       2. The optical apparatus of  claim 1 , wherein the shadow facet has an angle of grating of between approximately 20 degrees and approximately 50 degrees. 
     
     
       3. The optical apparatus of  claim 1 , wherein a first shadow facet of the respective shadow facets has an angle that is the same as an angle of a second shadow facet of the respective shadow facets. 
     
     
       4. The optical apparatus of  claim 1 , wherein the curve is an elliptical curve or a Roland curve. 
     
     
       5. The optical apparatus of  claim 1 , wherein the optical apparatus is a multiplexer or a demultiplexer. 
     
     
       6. The optical apparatus of  claim 1 , wherein the curved echelle grating is internally reflective. 
     
     
       7. The optical apparatus of  claim 1 , wherein the shadow facet is to reflect the light back towards an input waveguide coupled with the optical apparatus. 
     
     
       8. An apparatus comprising:
 a light source; 
 a waveguide coupled with the light source at a first side of the waveguide, the waveguide to propagate light from the light source; and 
 an optical apparatus coupled with the waveguide at a second side of the waveguide opposite the first side, wherein the optical apparatus includes a curved echelle grating; 
 wherein the curved echelle grating includes a plurality of grating teeth, a grating tooth of the plurality of grating teeth with a grating facet and a shadow facet, a light from the waveguide strikes the shadow facet of the grating tooth, and then is reflected in a direction not directly towards the waveguide to reduce interference with the light from the waveguide, and wherein the shadow facet has an angle of grating greater than 0 degrees and less than approximately 60 degrees with respect to a normal of a curve of the curved echelle grating. 
 
     
     
       9. The apparatus of  claim 8 , wherein the shadow facet has an angle of grating of between approximately 20 degree and approximately 50 degrees. 
     
     
       10. The apparatus of  claim 8 , wherein a first shadow facet of respective shadow facets has an angle that is the same as an angle of a second shadow facet of the respective shadow facets. 
     
     
       11. The apparatus of  claim 8 , wherein the curve is an elliptical curve or a Roland curve. 
     
     
       12. The apparatus of  claim 8 , wherein the optical apparatus is a multiplexer or a demultiplexer. 
     
     
       13. The apparatus of  claim 8 , wherein the curved echelle grating is internally reflective. 
     
     
       14. The apparatus of  claim 8 , wherein the shadow facet is to reflect the light back towards the waveguide. 
     
     
       15. A method comprising:
 positioning a two layer hard mask on a semiconductor layer, wherein the mask defines a curved echelle grating with a plurality of grating teeth, wherein respective grating teeth of the plurality of grating teeth include a grating facet and a shadow facet, a light from a waveguide strikes the shadow facet of a grating tooth, and then is reflected in a direction not directly towards the waveguide to reduce interference with the light from the waveguide, and wherein respective shadow facets have an angle of grating greater than 0 degrees and less than approximately 60 degrees as measured with respect to a normal of a curve of the curved echelle grating; 
 performing a dry etch; and 
 removing the mask. 
 
     
     
       16. The method of  claim 15 , wherein the mask include a thin silicon nitride (Si3N4) layer and a silicon oxide (SiO2) layer. 
     
     
       17. The method of  claim 15 , wherein the dry etch is a silicon dry etch. 
     
     
       18. The method of  claim 15 , wherein the shadow facet has an angle of grating of between approximately 20 degree and approximately 50 degrees.